/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* vim: set ts=8 sts=2 et sw=2 tw=80: */ /* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ #ifndef mozilla_DynamicallyLinkedFunctionPtr_h #define mozilla_DynamicallyLinkedFunctionPtr_h #include <windows.h> #include <utility> #include "mozilla/Attributes.h" namespace mozilla { namespace detail { template <typename T> struct FunctionPtrCracker; template <typename R, typename... Args> struct FunctionPtrCracker<R (*)(Args...)> { using ReturnT = R; using FunctionPtrT = R (*)(Args...); }; #if defined(_M_IX86) template <typename R, typename... Args> struct FunctionPtrCracker<R(__stdcall*)(Args...)> { using ReturnT = R; using FunctionPtrT = R(__stdcall*)(Args...); }; template <typename R, typename... Args> struct FunctionPtrCracker<R(__fastcall*)(Args...)> { using ReturnT = R; using FunctionPtrT = R(__fastcall*)(Args...); }; #endif // defined(_M_IX86) template <typename T> class DynamicallyLinkedFunctionPtrBase { public: using ReturnT = typename FunctionPtrCracker<T>::ReturnT; using FunctionPtrT = typename FunctionPtrCracker<T>::FunctionPtrT; DynamicallyLinkedFunctionPtrBase(const wchar_t* aLibName, const char* aFuncName) : mModule(::LoadLibraryW(aLibName)), mFunction(nullptr) { if (!mModule) { return; } mFunction = reinterpret_cast<FunctionPtrT>(::GetProcAddress(mModule, aFuncName)); if (!mFunction) { // Since the function doesn't exist, there is no point in holding a // reference to mModule anymore. ::FreeLibrary(mModule); mModule = nullptr; } } DynamicallyLinkedFunctionPtrBase(const DynamicallyLinkedFunctionPtrBase&) = delete; DynamicallyLinkedFunctionPtrBase& operator=( const DynamicallyLinkedFunctionPtrBase&) = delete; DynamicallyLinkedFunctionPtrBase(DynamicallyLinkedFunctionPtrBase&&) = delete; DynamicallyLinkedFunctionPtrBase& operator=( DynamicallyLinkedFunctionPtrBase&&) = delete; template <typename... Args> ReturnT operator()(Args&&... args) const { return mFunction(std::forward<Args>(args)...); } explicit operator bool() const { return !!mFunction; } protected: HMODULE mModule; FunctionPtrT mFunction; }; } // namespace detail /** * In most cases, this class is the one that you want to use for resolving a * dynamically-linked function pointer. It should be instantiated as a static * local variable. * * NB: It has a trivial destructor, so the DLL that is loaded is never freed. * Assuming that this function is called fairly often, this is the most * sensible option. OTOH, if the function you are calling is a one-off, or the * static local requirement is too restrictive, use DynamicallyLinkedFunctionPtr * instead. */ template <typename T> class MOZ_STATIC_LOCAL_CLASS StaticDynamicallyLinkedFunctionPtr final : public detail::DynamicallyLinkedFunctionPtrBase<T> { public: StaticDynamicallyLinkedFunctionPtr(const wchar_t* aLibName, const char* aFuncName) : detail::DynamicallyLinkedFunctionPtrBase<T>(aLibName, aFuncName) {} /** * We only offer this operator for the static local case, as it is not * possible for this object to be destroyed while the returned pointer is * being held. */ operator typename detail::DynamicallyLinkedFunctionPtrBase<T>::FunctionPtrT() const { return this->mFunction; } }; template <typename T> class MOZ_NON_PARAM MOZ_NON_TEMPORARY_CLASS DynamicallyLinkedFunctionPtr final : public detail::DynamicallyLinkedFunctionPtrBase<T> { public: DynamicallyLinkedFunctionPtr(const wchar_t* aLibName, const char* aFuncName) : detail::DynamicallyLinkedFunctionPtrBase<T>(aLibName, aFuncName) {} ~DynamicallyLinkedFunctionPtr() { if (!this->mModule) { return; } ::FreeLibrary(this->mModule); } }; } // namespace mozilla #endif // mozilla_DynamicallyLinkedFunctionPtr_h